Control system for hydraulic presses



1954 F. c. BIGGERT, JR

CONTROL SYSTEM FQR HYDRAULIC PRESSES 2 Sheets-Sheet 1 Filed March 18, 1948 HANDLING MOVING HEAD STATIONARY HEAD ADJUSTABLE CHOKE AC C U MULATOR HA DUNG FROM mm PUMP INVENTOR.

1954 F. c. BIGGERT, JR 2,666,292

CONTROL SYSTEM FOR HYDRAULIC PRESSES Filed March 18, 1948 204 m i, W

2 Sheets-Sheet 2 IN VEN TOR.

Patented Jan. 19, 1,954

Florence G. Biggert, Jr., Pittsburgh, Pa., assignor l J .toUnited' Engineering & Foundry l Company,

' Pittsburgh ran acorporation" of Pennsylvania Application March'18, 1948, Serial No. 15,613

reclaims. (c1. sk -51) J .This invention mates a a improvement hydraulic controls,and while'not-necessarily so' limited, pertains more particularly toacontrol system forfforging presses; and especially hy-- draulic presses of a typecommonly referred to as direct pumping presses); 'Presses of this type are presses in which theijhydraulicpressure for effecting their pressing operation is supplied directly from power-drivenpumpa'the pressure delivered to the press by the pumps being determined,- up to the extent of the pump capacity, by the resistance encountered by the movable press head r,

One object of the invention istoj provide a control which is capable of increasing the speed of operation'of this ty of pressand which is of considerable advantag'ein heavy'dutypresses;

Anotherobject of the invention is'to improve the means available'tothe operator of presses of this character for h'olding a'work' piece at a selectively controlled pressure between the press heads, which is highly desirable for various reasons and especially when it is'necessary' to 'A further object is to provide forfl'easily'and dependably immobilizing the moving press head at any selected point in its stroke. 7

"It is also an object to' provide a control ofthis {character which lend's'its elf to the utilization of improved features of design in the press itself These and various other objects, as well as numerous other featu'res'ahd advantages or the in shift the handling equipment associated with the vention, will be'readily-apparent amass skilled in the art'when the followingdescription' of the embodiments of the inventions therein illustrated is read in conjunction with .the"accompanying drawings; '1 -r v r "Figure 1 is a schematic View partly'in section of one embodiment of the invention.

Figure 2 is a sectional view-of the servo-motor constructionrshown'in Figure 1L5; #Figures 3,- 4,5, 6, 7 and fi'areihorizontal sectional views taken on the lines IIIII I, -IV- -IV."

v v VI-VVI, vii-v11 and. VIII-VIII-respec- .tively of Figure2 and Figure S is a se ctional view of a modification of the valve assembly shown .Reterring, to,. Eigure 1;. of ,the drawings, refer; ence character I designates. generally an .h'y- (draulici press .offthe directpumping type which comprises af'fraine not shows-1's stationary head i i V andbal' 'ance cylinders '5; "A'plungero'r pistons operating in the main cylinder-:1 is connected to thc Qc'nter of ithef moving head to provide the. working pressuretherefor, and pistons I in the balance cylin ders fiare connected to opposite ends of the moving head 3for retrieving the movingvhead. ,7

For actuating the plunger :6 of the main cyl-.

inder 4 it is connected by a pipe 8 to a main pump 9" which is'driven by a motor not shown. Ina.

similar fashion the balance cylinders 5 jare connected by a, pipe .II to an accumulator 12 which is in turn connected bya pipe l3 'to an auxiliary pump 14 also equipped with a drivingmotor not shown. The auxiliarympump 14 supplies the desired pressurized fluid to theaccumulator l2 so that from the accumulator, fluid under constant pressure will be supplied to the pipe I I and thence to the two pull-back cylinders 5. By a proper regulation of the controls of .the pump Hl'de- I sired pressure maybe maintained within the ac- 'cumulato'r I: so that the combinationlof the.

two serve ariav constant pressure source.

While other mcansmay be employed for such purpo ein the systemshown, asingle sump I 5 is provided for supplying and storing the hydraulic fiuidl used in th'e system. This sump, as indie cated, is connected by 'a'header I6 to both the main pump 9 and the auxiliary pump 14, and may beeither elevated or provided with a means not shown toestablish in it a desired static pressure.

A, valve assembly all is interposed in the supply lineB between the main pump 9 and the main cylinder 4 to control theflow of water from the main pumptothe main cylinder, and back to the 1 sump, I 5. .pipe. l8 is connected between the valve assembly I If and the sump, IE to control, in .a manner which will bepresently explained,

the flow of'water toand. from the valve assembly and the sump-f I To prevent v over-loading of the main pump .9,v

which is preterablyof a constant discharge type,

a; Joy-pass 19f having init a relief valve 2| is connected between the main line 8 andthereturnline liito the sump lli. Whi1e this relief valve which determines the maximum output pressure of themain'pump' may take various forms, the

cpnstruction disclosed in the present inventors Unit Sta es, a n ..a p cati n' Serial '765,'1 2 5,"'filedUuly '31; 1947, and issued as Patent,

No. 2,571,0Q7 on October 9 1951,, is recommended forrthispurpos'ell j Referring in" detail "atheifvav assemm fife main housing 22 is provided in which there is a'l suitably' formed; passage orduct 8a comprising that part of the" "main line 8' extending through the valve assembly. Also formed in the housing 22 is a duct |8a which is connected to the sump return line l8 and which terminates in the housing 22 in an enlarged opening 23. This latter opening 23 is connected by a duct 24 with the main line duct 81: to provide a flow connection between the main cylinder 4, the main pump 9, and the sump l5. In order to regulate the flow between main line duct 8a andthe return flow duct |8a a shut-oil and throttling valve 25 is po-' sitioned in a bore 26 communicating with the enlarged opening 23 at the inner end of the re turn flow duct I8a, and is so arranged as to seat on the upper end of the duct 24 which connects the main line duct 8a with the return flow duct |8a.

For controlling the flow between; the balance.

cylinders and the main cylinder through the main line duct 8a of the valve assembly H, a valve 21 is arranged to operate in a bore 28 which intersects the main line duct 8a and to seat-when closed on the upper endof a smaller duct 29a. Thi latter duct 29a has connected to it a pipe 29 which is in turn connected to, the pipe. I connecting the balance cylinders of the press with the accumulator l2 which supplies their operating pressure. At the point Where the bore 28 for the main line valve 21 intersects the main line; duct 8a the main line duct is enlarged as indicated at 3| to permit a flow through the main line duct around the main line valve 21..

Mounted on supports 32 on the valve housing 22 in line with the bore 28 for the main line valve 2.! there is arranged a cylinder 33 for controlling the movement of the mainline valve 27*. The piston 34 of this cylinder is equipped. with a piston rod 35' which i fitted in a bore 36 communicating with the bore 28 for the main line valve 21, and has its free end disposed to rest on the top of the main line valve 21. Underneath, this cylinder 33 a coil spring 31 is fitted on the piston rod 35. and is adapted to normally bias the main line valve 21 to its closed position. To perform this function the upper end of this spring 31 is rested against the bottom of the cylinder 33 and its lower end against a fitting 38. secured to the piston rod 35. This spring is provided with suflicient tension to hold the valve 2 closed when the throttling or return-flow valve is open and there is little or not any pressure in 8a. To permit adjusting the tension in the spring 3'1, the fitting is arranged to rest on an adjustable nut 37a threadably secured to the rod 35, and between the top of the bore 28 andv the. duct 8a. a. bleed duct 28a is provided.

The object of the cylinder 33 more specifically is to provide, as may be needed in the functioning of the system, for relieving the. pressure imposed on the main line valve 21 by the rod through the influence of the spring 31. To accomplish this, a liquid supply line39 is connected to this cylinder 33 and to. a suitably controlled pressure supply which in this instance, although it could be otherwise arranged, is. furnished by the servo-motor 4|.

In light presses the return-flow throttling valve 25 may be. operated directly from an operating lever, or by other means not shown. For heavy.

duty presses, however, a servo-motor such as, the servo-motor 4| or the like is desirable for this purpose.

The primary duty of this servo-motor 4| is to control in the main cylinder exhaust circuit the operation of the return-flow and throttling valvev 25 contained therein and located in the p turn line duct [811. To so function it is mounted.

. 4 on supports 42 secured to the valve housing 22 with its piston connected by a connecting rod as to the throttling valve 25. The operating pressure for this ervo-motor is supplied by a pump 44 actuated by a pump motor not shown and connected thereto by inlet and exhaust lines 45 and 45 respectively. For controlling said servo-motor a control element 4! connected to a pivoted operating lever 48 by means of a floating lever connection consisting of a lever 49 and a link 5|. The lower end of the lever 49 is pivotally connected to the outer end of the servo-motor control element 41', and the ends of the link 5| are pivotally connected to the lever 49 and to the control lever 48,.

The free, end; of the lever 49 is equipped with aroller 52 that is arranged to bear on a cam 53 which is actuated by the movement of the movable press head 3, the roller 52 being held in contact with the cam by a coil spring 55- mounted between it and a support 55. The curvature of. cam 53 is such. that inaccordance with the movementr of the press head the roller 52. in contact with the cam moves a proportional amount and the diameters of the sprockets 51 and 59 are so related that the cam roller will be moved from its minimum to its maximum position when the press head moves from. its top to its lowermost position of its stroke.

As. shown, although the equipment for this purpose may take other forms, the cam 5-3 is secured to a shaft 56 or to a. sprocket wheel 5.: mounted on the shaft 56. Around this sprocket wheel 57 there is mounted a chain 58 which is extended in one direction over an idler 53 and connected to the moving press head 31 and. in the. other direction over another idler 6| and connected to a counter-weight 62. With this arrangement when the. press head is moved down-ward, the cam 53 and the sprocket 5.1 are caused to move in a counter-clockwise direction by the press head 3, and when the-press head is. raised, they are caused to move in. a clockwise direction by the counterweight 62. Thus irrespective: of the position of the servo-motor control. lever 48, the position of the servo-motor control element 41 is influenced by the position of themoving pres head. For reasons which will presently be made more apparent, the cam 53 is generated on a curve which imparts tothe roller 52 on the lever 49 as the cam is rotated a displacement relative to the cam. center which is substantially directly proportionate to. the distance which the. movable press. head 3 moves relative. to the fixed press head 2 when theformer is actuated.

While other designs of servo-motors may be used, the servo-motor 4|. is; a constant-flow type of motorsimilar in general principles to that disclosed in the present inventors Patent No. 2,370,137, but widely varyihginconstruction. As shown in Figures 2 ta. 8,. this motor comprises principally a combined cylinder and housing 63, a piston 64, an internal multiple valve 55, and a valve-controlling element 41-. At its upper end the housing 63 has an enlarged main cylinder bore 66 and is provided with a detachable head 61 held in place by bolts 38". In this main cylinder bore 63 the main piston 64 of the motor is arranged for reciprocal movement. Depending from themain piston. is. an elongate reduced.

tion 64a.

In the lower end of the multiple valve 85there is arranged a fitting 12 which is-pr'o'vided with a diagonal bore 13. In axial alignment within this bore 13 a somewhat larger bore 14 is ex-. tended through the piston extension 64'af'The purpose of the bore 13 is to receive an angular-1y" displaced extension 41a secured to the imler end of the valve-actuating element 41. Consequently as the valve-actuating element 41 is displaced I axially by the actuating lever 48 or thecam'53,

the multiple valve 65 is'correspondingly move with respect to the piston extension 64a,-such a 15 relative movement being permitted due to the bores 14 in the extension 64a being larger than the bore 13. r i

To permit the assembly of the multiple valv e 65 in the piston extension 6411, the bore' is extended through the bottom of the piston exten: sion 64a. The lower end of this latter bore H is provided with internal threads 15 for receiving the externally threaded end. of the rod43 which passes through a bore 16 in the lower end of the housing 63 and is connected to the throttling valve in the return-flow duct i8a of the valve assembly housing 22.

For housing and supporting the valve-actuating element 41, a laterally extending projection 71 is formed on the housing 63. This projection 11 has in it an axially extending bore 19 which communicates with the vertical bore 69in the housing 63, and in it there is inserted acentrally bored fitting 8| in which the valveeactuating elementis mounted, being securedto the outer end of the projection T! by bolts 82.

The multiple valve 65 is equipped with three axially spaced valve sections 83, 84, and 85, which have a diameter permitting them to fit snugly in the internal bore H of the piston extension 64a, the balance of the valve element65 having a lesser diameter to allow fora flow of,

the motor-actuating fluid'around the valve ele,- ment 65 between and belowthe valve sections. A central bore 65a is provided in the body of. the

multiple valve to equalize pressure on the ends.

of the valve.

The centrally disposed valve section 84 is em ployed to control the flow of the actuatin fluid from the servo-pump intotheservomotor,

To accomplish this the inlet pipe 45 fromthe servo-pump is connected to a port 86 whichcommunicates with an annular groove 81' formed in the inner wall of the housing 63 opposite the valve section 84. This groove 811s in turn 'con-.

nected by radial ducts 88 in the pistonextensionj 64a with an annular groove 89 formed in the.

bore H opposite the valve section 84 To function as required the axial length ofthe valve section 84 is made less than theraxial width. of.

the groove 89. Thus when thevaIve'sectiOn is centered with respect to the groove 89, as it.is When the servomotor isin its neutral position,

the inlet fluid is permitted to. flow both upwardly:

and downwardly of the body of the valve element 65in the bore H.

The valve sections 83 and 8 5 are employed 7 control the flow of the actuating fluid from'the servomotor-back to the' servo-pump fl by, way, of the return-flow pipe 46. Towardthis end an 9| is formedin the inner wall of. I

annular groove the housing 63 opposite the valvesectionfiii, and

an enlargement92 is which extends from a point abovethe valvelsec: tion 85 to the bottom of the bore 69. Also adjaprovided inthe housing 68.

valve sectio'ns 83 iand fa'r so proportioned and arranged that'when the valve section 84 is centered'an opening"exists'between'the lower edge of groove 93 and the bore H, and also an opening between the upper edge of groove 94 and the bore II. This relationship, however, is such that when valve section'84is moved to close 011 the lower edge of theadjaceiit groove 89 from bore 1 I valve 83 will close off, its adjacent groove '93 from bore "H and valve85 will increase the opening between itsadjacent groove 94 and bore H. Conversely when valvesection 84 is moved up-. wardly t'o shut .oif. the upper edge of groove89 from the bore l valve,section 85 will close ofl groove 94 f'rom bore ll and increase the opening between groove 93 and bore". a a

Between the internal grooves 93 in the .bore H and9l in the bore 69 adjacent valve section 83 there are formed. radially disposed ducts 95 which permit a flow of fluid from the groove. 93 into the groove 91.. This latter groove 9| in turn communicates with apart 96 to which the exhaust or returnline .49 from .the servomotor to the servo-pump is connected Similarly, between the enlargement 92in the bore 69 .and the groove .94 adjacent thevalve section 85 there are formed radially disposed ducts 91 which permit a flow of fluid from the groove 94 into .the enlargement 92 of the bore 69, which in .turn communicates with a port 98 that is connected v by a pipe Mic with the servo-pump return-flow pipe46. J

For allowing the actuating fluid to flow from the servo-pump into the cylinder bore 66 at the top. of the piston. 64 of the servomotor, a duct I 0| is formed in the piston 64 with its upper end terminating at the top of the piston and its lower end communicating. with the internal bore 1| substantiallyi midway between the annular grooves93 and.89 opposite th'e valve sections 83 and 84 respectively. Similarly, for allowing the actuating .fiuidv toIflow from the servo-pump to the cylinder'bore 66 at the-bottom of the piston 64,. a duct 1.02 is formed in the piston 64 with its upper end terminating in a circular groove H13 formed in the lower face of the piston 64, and its lower end communicating with the inter- 'nal. bore H substantiallymidway between the grooves 89 and 94. in the bore H adjacent the valve sections and 85 respectively.

As afurther feature of this construction ports I04 and |05 are provided in the cylinder wall 63 adjacent the upper and lower ends respectively of. the cylinder-bore 66 so that the fluid pressures existing at these points can be utilized, in additionto actuating the piston 64', for other control purposes aswill be presently explained. .As, illustrated in .Figure .1',.port 194 is connected by pipe 39 with the cylinder33 utilizedto counteract the influenceoi the .coilspring 3! which normally urges the main line valve 21 toward its closed position. In thisparticular construction port I05 is pluggedas it has no useful purpose but in the modified form of valve assembly this port is employed and serves adefinite purpose.

Accordingtothe construction. shown in F'ig "ures'2 to. 8 inclusive} when the multiple valve .85 is in its centralor neutral position, that is, when theinlet valve .section Sills centered with res.

spectito the adjacent groove .89, the. actuating fluid..from. the vservo-pumpflows through pipe of port 88, thence -through radial ducts 88 into groove 89. From theigroove 89 .part of the fluid flows over the top of the valve '84 into bore 1| from whence part thereof passes through duct lill into the top oi the cylinder bore 68, and the balance around valve 83' into groove 93, and out radial ducts 95 to groove 91, and by way of port 96 into retur-n line 46 back to the servopump. In a like fashion. part of the inlet fluid passes around valve '84 into bore H below the valvesection 84. Thislportion of the fluid flows in part, through =duc't 182 to the lower end of cylinder bore 68, whereby subjecting .piston 64 to substantially equal forces on its opposite sides, varying,-ot course, in accordance with the difference in their effective areas; the balance of the hind passing out the bottom of groove 89 flows through bore 1! around valve section w 85 into groove 94 from whence by way of radial ducts 91 is passes into the enlargement 92 of bore 59 and out port '98 to pipe 46a and into the return-flow pipe 46.

To raise the connecting rod 43 the control ele ment 41 is moved inwardly and to force it downwardly the control element 41 is moved outward. By these difierent movements of the control element 41 the multiple valve 65 is moved up or down as the casemay be with respect to the piston extensions 8411. Hence the valve sections 83, 84, and 85 are correspondingly moved with respect to the annular grooves in bore 1| adjacent to them. 7

If the control element 41 is moved inwardly and thus the multiple'valve 85 is moved upwardly, valve section 84 will tend to cause the inlet pressure to flow through duct I02 to the bottom of cylinder bor'e 56 beneath piston 64, and when moved 'sufiicienly will completely shut off the inlet flow to duct H11. In the same way valve 85 will tend to prevent the inlet pressure escaping through port 913 until moved sufficiently when it will stop it completely, while valve 83 will facilitate the escape of pressure from the top of piston 64 through duct Hll out through port 98 to the return-flow pipe 46. As a result pressure will build up on the lower face of piston (it and cause the latter to rise, raising the connecting rod 43 with it. As the piston raises, 7

however, the valves 83., 84, and 85 will be returned toward their neutral positions with respect to the adjacent grooves 93, 39, and s4 respectively, and as soon as this is accomplished no further movement of piston 64 will take place. When the control element 41 is moved outward, exactly the same operation or the piston occurs, but in the opposite direction and, of course, with attendant reverse flow into and out of the main cylinder bore 88 and the inlet and exhaust passages.

In such a servo-motor the fluid pressure acting on the piston thereof will vary according to the H resistance to movement which the piston encounters. when closing throttling valve 25, very little pressure will develop above the piston 54 until such valve is completely closed, but immediately upon its being closed, this pressure will rise to the pressure which the servo-motor pump 44 will develop. To prevent overloading of this pump a relief valve 40 is connected between the supply and return lines 45 and 45 respectively connected to this ump, and the setting of which will determine the maximum pressure the pump will deliver to the servomotor. While with such an arrangement a somewhat wasteful pump action is encountered when the -s'ervo=-motor is in stalled condition, this is not particularly objectionable for ordinary press operation because the duration of stalled periods is short. The constant flow pump is rec ommended because it is simple and cheap. When operations requiring long periods during which the servo-motor is stalled are involved, a radial piston or equivalent variable flow pump with zero discharge at maximum pressure may be used.

In accordance with the construction illustrated in Figure 1-, the pressure which develops in the top of the servo-motor cylinder 88 is communicated by the pipe 39 to the cylinder 33 employed to influence the operation of the main line valve 21. As previously explained, the rod 35 bearing against the top of this valve is not connected to it. It is arranged to rest only on the top of this valve. Under normal conditions when there is no pressure in the cylinder 33, the main line valve 2 1 is urged to its closed position by the spring 31, and this spring is provided with a sufficient tension to-hold the valve 221 closed against thepressure in the line 29 connected to the accumulator I2 which supplies pressure for the balance cylinders 5.

When the throttling valve 25 in the sump return line I8 is fully open, due to lack of pres. sure in the top of the servo-motor cylinder 65, there will also be a lack of pressure in cylinder 33 v On the other hand, when the throttling van/e25 is fully or practically closed, and under which circumstances a pressure must be establishedin the top of the servo-motor cylinder 65 which is sufficient to overcome the pressure in main pump line 8', a similar pressurewill be present in the control cylinder 3'3 tending to overcome the pressure of the spring 31. If the throttling valve 25 is fully closed, the pressure in the control cylinder 33 will be sufficient to cause the piston 34 which isattached to the rod 35 to compress the spring 31 and thus render the main valve 21 free to act as a simple check valve, but it will only act as such under these conditions. It is to be noted that only part of the pressure in spring 31 need be relieved in order that the 'main valve '21 may open, since the pressure in line 29 strongly urges this valve toward its open position. This is important to the operator's control of the main valve because it makes it possible through the use of the servomotor which controls the throttling valve 25 for the operator to exercise control over the open ingo'f the main line, interconnecting valve 21.

Whehthe throttle valve 25 is partially closed, only sufficient pressure is required at the top of piston 84 to ofiset the force produced on the bottom of the valve 25 by the pressure in the main pur'np line 8 and which will vary with the extent the valve is open.

To lift the incvable presshead 3, the pressure operated throttling valve 25 is opened and the interconnecting pressure operated valve 21 closed. This allows the water in the main press cylinder 4 and main pump 9 t6 eiihaust' through the throt tling valve 25 into the sump l5, and the pressure in the balance cylinders 5 effected by the accumulator to move the movable press head upwardly to the top o'f its strdke.

To movethe 'mov' me press head 3 down at a relatively slow speed. through proper actuation of the servo-motor 4| the main line pressure operated valve 21 is, completely closed and the pressure operatedth'rottling valve 25 is only partially cl'os'ed. This causes substantially all, but not all of the water delivered by the main pump 9 "to flowiinto the main press cylinder 4 and develop a pressure therein which is sufiicient to overcome the pressure in thebalance cylinders and move the press head downwardly.

' When a rapid lowering motion is desired, through proper actuation of the servo-motor 4| the throttling valve. 2-5 is closed entirely and the interconnecting valve 21 is opened. This allows thebalance cylinders to exhaust into themain press cylinder along with all of the water from the main pump,'with theresult that the motion of the movable headis speeded up because of the larger area of the main press cylinder. Since downward movement of the press headis opposed by the fluid in the balance cylinders; obviously to move the control lever 48 to the leftsufficiently to keep the throttling valve in the required position to cause the press head tomove upward. By the time the press head 3'reaches the top of its stroke,'the operator will have moved the control lever 48 to its farthest left position.

To move the movable press head 3 downward T'at a reduced speed, the operator moves the conthe rate at which the fluid escapes therefrom will 'be one of the factors determining the speed'at which the head descends.

When the movable press head engages the work on the fixed press head, the interconnecting 'valve .21 acting as a simple'check valve is closed by dropping due to its .ownweight into its closed position inasmuch as. the high fluid pressure which normally exists inthe line 29 duringv downward movement of the press is now relieved by reason of. interruption of rapid movement of the press head as it engages with a workpiece'so that the movable press head'will thereafter move down at normal pressing speed. c

To immobilize the movable press head, the throttling valve 25 inthe sump line Isa is so adjusted, in accordance with the operation thereof hereinafter set'forth, that a pressure willbe 7 established in the main press cylinder 4 which is just sufficient to counteract the pressure in the balance cylinders. Likewisewhen it is desired to hold the work between the press heads with a light pressure, as is desirable when shifting the handling equipment associated with the press, the throttling valve 25is adjusted, in accordance withthe operation thereof hereinafter set forth, to maintain in. the main press cylinder whatever pressure is required 'for this purpose.

' In accordance with this invention when it is desired to raise the'movable press head 3, the

control or handling lever 48 is moved to the left,

as shown in the drawings, the distance necessary to adjust the throttling valve 25 to its open position and allow thewater in the main press cylinder to flow into the sump I 5. This movement of the handling lever 48 lifts the valve 65 of the servo-motor upward and produces as previously explained a resultingupward movement of the piston and the throttling valve 25 which is connected to it by the connecting rod 43. 'With this trol lever 48 to the right 'sufiiciently to cause the servo-motor piston to move the throttling valve into a position with respect to its seat such that enough pressure will be supplied by the main pum 9 to move the press head downwardly against the pressure of the balance cylinders 5. In this operation of the servo-motor the high pressure in the servo-motor cylinder 66 is at the top of the piston 64, and although the pressure may balance or even be sufficient to draw the piston 34 upwards and compress the spring 31,

:is prevented due to the high pressure imposed nevertheless upward movement of the valve 21 upon the upper portion of the valve through the duct 28a connected to'the main line duct 8a carrying the full pumping pressure, which is sufiicient to oppose that resulting from the balance cylinders themselves. Consequently in this downward movement the press head is resisted by the full effect of the balance cylinder pressure,

and the down speed is determined by the pressure "delivered tothe main cylinder 4 as controlled by the throttling valve 25.

' As the press head 3 starts down the cam 53 actuated by the chain 58 attached to the press head is rotated in a counterclockwise direction.

This results in the cam 53 tending to readjust the valve element 65 to a position which, without adjustment of the hand lever 48, would cause the press head to be stopped. To avoid this the operator must continue to move the control lever 48 suiiiciently to overcome the compensating effect of the cam 53v to keep the press head moving. 7 When it'is desired to have the press head move downward ata rapid speed, the handling lever 43 is moved to the right suiiiciently to completely close the throttling valve 25, and thereafter this movement of the handling lever iscontinued sufiiciently to compensate for the offsetting action of the cam 53 so long as such downward movement is desired. Under these conditions the full operation of the servo-motor, the pressurein the the counter-weighted chain 58 passing around the sprocket 51carrying the cam 53, against which the end of the'control lever 49 bears, startsto rotate in'a clockwise direction. As this takes place, the spring 54'bearing against vthelever 49 moves the upper end of lever 491:0 the left as permitted by thecam 53 which results in lever 49 pivoting about the point where the link 51 is connected to it. This tends to move the control rod 4'! of the servo-motor in a direction to cause the servo-motor piston 64 to close the throttling valve 25. To overcome this the operator must continue efiective high pressure in the servo-motor is at the top of the piston 84 and this pressure, which is communicated to the control cylinder 33 for the .main press valve 21, is sufficiently high to cause the piston 34 in that cylinder to so compress the spring 31 which urgesthat valve closed, and due to the difference in the area between the main press cylinder and the two balance cylinders, the main press cylinder being the greater, the main press plunger will move downward and, as the intensity of the pressure from the balance cylinders imposed upon the lower portion of the valve 21 is so much greater than that which is imposed by the pump on the top portion of the valve 21 tending to keep it closed, the valve 21 consequently will open and permit the fluid being expelled fromthe balance cylinders to enter th'e line leading to the to of the main press cylinder. I

into t emain press cyiind ressure, to build" up" rapidly. This: pressing action i the a asw ll, bev apparent, Wh n 'th Pres a is we e tg n jae ment with the work t a r duc d sp d a in. a h instameit continue the press a tiQnthecontrQl lever'QB 1 ,0

seme

must be mo d vfi ri l t r to WaYS-Q mm servo the m n n wi i t e .3- throt ling: velr 25a ts fully open Rest 11.- When it is desired toimmobilizethe press head This setqj con exists when the contrql at any selected positidnbetweenthe two extremfirst thiqfifilev W9 leve s qn tor. move Qsfs l t d p si ionic ine dingw t in dfin the same iresi en. at. a s eed "ch iti'es of it stroke, the control lever 48 is held 15 {5d sue the e t n t w f f s. he t t e eeds i s; emnsesetin ectionor the 53- head. Thereafter, depending on the direction of With this arrangement the additional throttling mov men ofthe headyasthe head mdv siow'srd valve. HQ isqpe sd, only when h rare ure is such position, the eamiii will so, adjustthe valve g0 sufiic ent to ma n the first throttling valve eleme 6 a fi i NONI-131? s m l- 2 1 v i iiiq if e h ii 'es lie'si3t esrv mo 41 o ma ntain the: thrott e valve 25 r e hi h r speed bec use thevr is anseto in e o o requi ed' o 'th press head to flq oi. w ter m hs: ma n pres cylinder n ch' i Sh u d the pre s head; tend to intg thesum 5 is t e eby educed pass such position, the cam 53 d'us'ts the: Ne .25 Withothis valve ol assembly, slow liiting ele n 65 to m ls h nee 1 o or the Pre s. d i btained. by'dn nine daily Referring to Figure 9, a mqdlfied form of valve the. first 'throt g'va ve 25a By u in t shug'h assembly IIa'is shown which has for its principal Valli/T68 tl eft fllev l' i a tfid d eotly the servoobjects'to provide for making it possible tolraise motor Ma m y be made Smaller nhe' e s. h at a aster p to redue the 3. er r. ne essary hen: Only one 5 .1.01; lve s forces required of the servo-motor, and t'o' afford used l o, th orqe e ded n the ervqfinqtor amore sensitive throttlin control. In this figure 10! or 912.81%? ii? this 5 mil IQlVQ Q91 for purposes of description the parts. of thefas pondingly'sma T ifimhkfi f9 mere r semblv which are similar to the parts of the assembly I! illustrated inFigure l are identified y t am reference har ct rs. but have the suffix a added to them.'

The principal differencehetween the assembly five qon rq fof the pr Fla and the assembly 11 is'th t (agrarian-d larger throttling valve q provided in he sunip return line {8. As shown; this, addit na v'flv e H0 is arranged in a bore Ill, whi hjcomates with. a amber 112, t th end: Q? an s n wdajo h e, 8, s e ts 0 he ppe en f bo e swhisn nne s he i;- ber H 2 with the main line duet Bea.

To qrmany' hold he ad t n l hr t lin valve H0 on its seat, it is prov'ided t it u r endvvithja piston I I} 'whlchjislocat. 1 a. der H5 m unted on thehQllSig 22,, by s my force to perforn itsiunctiqns. the" cylinder q e edt r y 5117 flu d" pp y such as an a xi ia ysc umu latqli 9 for example, the'ac'cumulatpr l2 illustrated in Figure 1, As will be obvious, since this Ive functions quite sirnilarly to the; gain lie valve 21a, a spring arrangement such as; usedfinthe main line valve anddesignated by. numerel 31d and 3'Iaa mayjbeused instead of the piston cy nd "a r g me tl or le m ly r n i valve H0 toward its 'closed DQSitiO'n'.

For opening the valve Ill! Whenitis desired 1 to impart rapid lifting movement to"v the pre s hfi fins fi head; a i r H i secured o the housing 22;: an ing'l cylin by supports n. Inthis, Qyn derapis |,|s;i1fs

located'which is connected tooth eplblw r sendfq f the valve uu byarod {2| which extendsthro'ngh b rg} i i v i i ssbslans rl n s .m in$v mde V those kille insert .1 w ll t e, obv ous va ve Zl'anjd -Zfiqareoisuih 1Z9! the fp h (2 9 here uir d fl ng; and. pm e ses: itis r reierable to o n on Th ee he i es siie b fishers: pteierebles his abore 122 in the housing in alignmentwith the aki'sof the valvellp. This latter Icyli'nder III 7 is connected by arpipe l23to the port "15 co n municating with the'jl'ower end or thecyIiri j bore 56 in the servo-motor, Withthiis arran ment whatever pressure. is supplied to the 1b er Side e r o-motor..b s mf i s u. w im the type in which rapid lowering 'of'the' press head is accomplished by interconnecting the balance cylinders and main cylinder, which consists'in choking or throttling the flow through this connection to allow freedom of design as regards size of balance cylinders and hydraulic pressure in the balance systemwhile maintaining suitable speeds of raising and lowering movements.

Although other means for such purpose may be utilized, the valve 20,,as shown, comprises a housing I3I provided adjacent its opposite ends with an inlet port I32 and outlet port I33 and a centrally disposed partition I34 in which a bore I35 is formed for thereception of an adjustable valve element I36. This valve element H6 is mounted on a stem I31 which is threadably fitted in the base of the housing and equipped with a hand wheel I38 for adjusting the valve element. p

It is to be appreciated that the construction herein disclosed may be widely modified for purposes of fabrication or for other reasons without departing from the spirit of this invention. In this connection, for example, in order to afford the operator a better feel of the assistance provided by the servo-motor, in place of having the valve sections 83 and 85 operated with a sliding fit in the bore II of thepiston extension 64a, they may be designed to effect a seat in the bore TI. This, of course, would involve providing'a bore II with .diiferentinside diameters and the extension 64a, as well. as the valve element 65,

.being made in section iniorder to effect the assembly. This modification is not illustrated as it is deemed to require, in the light of this disclosure and the teaching of Patent No. 2,370,137,

nothing more than ordinary mechanical skill.

According to the provisions of the patent statutes, the construction and operationof the invention has been illustrated and'described in connection with a recommended embodiment. It is desired that it'be understood, however, that within the scope of the appended claims the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A control system for hydraulic presses equipped with a main piston-cylinder assembly and a balancing piston-cylinder assembly for the movable head of the press, the main cylinder having an area greater than that of the balance cylinder, comprising a source for supplying a constant volume of fluid at varying pressures connected to the main cylinder, a constant pressure source of fluid for the balancing cylinder, a fluid pressure operable valve interconnecting the balancing cylinder and the main cylinder to effect rapid lowering of the movable press head, yieldable pressure means disposed to normally urge said interconnecting valve towards its closed position, and other pressure means which-is selectively operable for offsetting the efiect on said interconnecting valve of said first-mentioned pressure means.

2. A control system according to claim 1 which is equipped with a by-pass valve for diverting fluid supplied to the main cylinder, and means for rendering the operation of the valve interconnecting the balance cylinder with the main cylinder dependent upon the pressure acting upon said by-pass valve and so operative as to prevent opening of the interconnecting valve when the proper. functioning of. the press requires itto be closed'.'

3. A control system according to claim 1 in which the interconnecting valve is arranged to be opened by the pressure of the fluid supplied to the balance cylinder, yieldable means normally urging said interconnecting valve toward its closed position, a by-pass valve for diverting fluid supplied to the main cylinder, and means coordinated with the movement of the by-pass valve for offsettin the effect 'upon the inte connecting valve of the yieldable means normally urging the interconnecting valve toward its closed position.

4. A control system according to claim 1 in which the interconnecting valve is arranged to be'openedby the pressure of the fluid supplied to the balance cylinder, yieldable means normally urging said interconnecting valve towards its closed position, a by-p'ass valve for diverting fluid supplied to the main cylinder, a servomotor for operating said by-pass valve, and means for utilizing the servo-motor to offset the effect of said yieldable means upon. said interconnecting valve and so disposed that the operation of said interconnecting valve and said bypass valve is coordinated by said servo-motor.

5. A control system accordingto claim 1 which is equipped with a by-passvalve for diverting fluid supplied to the main cylinder, a lever for operating said by-passf valve, and means for modifying the action of said lever to immobilize the movable press head at points within its stroke approximately in proportion to the position of said lever within the latters stroke.

6. A'control system according to'claim' l which is equipped with a by-pass valve for diverting fluid supplied to the main cylinder, a lever for operating said by-pass valve, andmeans for automaticallymodifying the effect of said by-pas's valve lever upon said by-pass valve to produce a pressure in said main cylinder sufficient to counteract the force of the balance cylinder to poise the movable press head at all positions of said lever.

'7. A control system according to claim 1 which is equipped with a choke arranged to regulate the flow of the fluid discharged from the balancing cylinder into the main cylinder to control the lowering speed of the movable press head.

8. A control system according to claim 1 which is equipped with a pair of fluid circuits for bypassing the fiuid pressure supplied to the main cylinder, a valve in each of said by-pass circuits for controlling the flow through them, a servomotor for opening and closing one of said bypass valves, a power unit for opening the other of said by-pass valves, and a connection between said servo-motor and said power unit for rendering the operation of said power unit dependent upon the operation of said servo-motor.

9. A control system for hydraulic presses equipped with a main piston-cylinder assembly and a balancing piston-cylinder assembly for the movable head of the press, the main cylinder having an area greater than that of the balance cylinder, comprising a source for supplying a constant volume of fluid at varying pressures connected to the main cylinder, a constant pressure source of fluid for the balancing cylinder, a valve for interconnecting said main cylinder and said balancing cylinder to effect rapid lowering of the movable press head, yieldable pressure means for normally urging said interconnecting valve toward its closed position, a bypass valve for bytsetse passing the fluid normally delivered to the main cylinder, an hydraulic servo-motor ,for actuating said by-pass valve, a control element for controlling the operation said servo-motor, a pressure-responsive element for rendering ineffective the pressure means provided for urging said interconnecting valve to its closed position, and means connecting said servo-motor to said pressure-responsive element for utilizing the pressure in the servo-motor to actuate saidpressure-responsive element to adjust the yieldable pressure means for the interconnecting valve when the servo-motor is operated to close the throttling valve and thereby facilitate the opening of said interconnecting valve.

10. vA control system according to claim 9 which is equipped with a displacing element for moditying the action of the control element for the servo-motor, anda drive for said displacing element actuated by the movable press head of the press.

11. A control system according to claim 9 which is equipped with a cam for modifying the action of the control element of the servo-motor, and which has an operating surface so formed as to bear a direct relation with the various positions of the movable head of the press.

12. A control system, according to claim 9 which is equipped with an hydraulic motor torrendering inoperable the pressure means provided for urging the interconnecting valve toward its closed position, and a fluid connection between said hydraulic motor and said servo-motor arranged to employ the hydraulic pressure in the servo-motor to energize said hydraulic motor.

'13. A control system for hydraulic presses equipped with a main piston-cylinder assembly and a balancing piston-cylinder assembly for the movable head of the press, comprising a source of fluid pressure for the main cylinder, a source of fluid pressure for the balancing cylinder, an

. 16 interconnecting valve ior connecting the pressure supply for the balancing cylinder with the pressure supply for the main cylinder, a spring mounted on said interconnecting valve and arranged to normally urge said valve to its closed position, a power unit connected to said spring to render the springs action on the interconnecting valve ineffective when the power unit is energized, an exhaust circuit for the main cylinder of the press, a Joy-pass valve disposed in said exhaust circuit, a servo-motor for actuating said by-pass valve and for energizing said power unit, and control means for regulating the operation of .said servo-motor.

FLORENCE C. BIGGERT, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 523,419 Thorpe July 24, 1894 1,716,010 Smeby June 4, 1929 1,816,829 De Leeuw Aug. 4, 1931 1,822,690 De Leeuw Sept. 8, 1931 1,955,278 Ferris et al. Apr. 17, 1934 1,990,052 Sosa Feb. 5, 1935 2,005,018 West et al. June 18, 1935 2,016,654 Shippy et al. Oct. 8, 1935 2,206,957 Hose July 9, 1940 2,282,977 Mast May 12, 1942 2,320,759 Stacy June 1, 1943 2,337,848 Davis Dec. 28, 1943 2,346,214 Flowers Apr. 11, 1944 2,349,804 Sorensen May 30, 1944 2,360,060 Iversen Oct. 10, 1944 2,367,009 Davis Jan. 9, 1945 2,376,519 Stacy May 22, 1945 2,403,391 Muir July 2, 1946 2,449,400 Lindsey Sept. 14, 1948 2,564,285 Smith Aug. 14, 1951 2,568,042 Vltavsky Sept. 18, 1951 

